Interesting. I ran Quickload for 270 Winchester with an 18" barrel and 55000 psi max. In other words, taking everything out of the equation except the case capacity. Ended up with around 2860 as max velocity with a 130 Berger with a number of powders (RE 25 showed another 20 fps, but there are a bunch right around 2850-2860).
Did the math (and keep in mind this is using the case capacities the OP gave us for the 270AR, so things could vary a bit in real life). Ended up with around 260 fps less than the 270 Winchester.......or 2600 fps.
